Endorsement printers constitute an essential part of many high-speed document processing systems, such as item processors and check sorters, for example. Such printers can imprint various information on the backs and fronts of checks, such as endorsement statements, bank name or other identification, date, etc. Document processing systems of this type are normally designed for a long effective life, such as one hundred million cycles or more, and it is important that the various elements of such systems be capable of long-term reliability with minimum downtime for repair.
Endorsement printers are generally either of the continuously operating type, in which the endorsement printing element is continuously rotating, or of the intermittent operating type, in which the endorsement printing element operates only when a document has been transported to the printing position.
Continuous operation has certain advantages in terms of minimizing acceleration and deceleration of the printing elements, so that some wear and tear on these elements attributable to starting and stopping is avoided. However, there are also disadvantages in this type of system. One of these is a tendency for this type of system to cause undesired ink markings on the documents being processed, since the ink supply roller is in constant motion, and ink is continuously being applied to the printing element. Another disadvantage is that selection of the location of printing by the stamp on the document is difficult or impossible in the case of a continuously rotating system. Furthermore, the fact that the system is continuously operating does tend to increase certain types of wear.
Intermittent operation avoids the above disadvantages, but tends to subject the apparatus to shock loadings, from frequent starts and stops. Also, the intermittent operation tends to be noisier than continuous operation. Existing intermittent operation apparatus may use a clutch to give controlled initiation of the printing sequence for controlled location on the document, but may suffer from electromechanical reliability problems, due to the high accelerations and decelerations involved. Other alternatives include the use of a stepping motor or a D.C. servo motor to rotate and control the endorsement printing element. This requires a large, costly motor, due to the force which must be supplied during the inking and printing cycles, as well as forces required for acceleration and deceleration.